Cooking surfaces of this type have been disclosed in German Auslegeschrift No. 24 40 701 and German Offenlegungsschrift No. 26 41 274. They have a gas-heated radiant burner comprising a burner plate which is provided with a radiant surface which is arranged at a small distance from the glass ceramic plate and heats it. The gas burner is operated intermittently, i.e. is turned on and off at a predetermined rhythm depending on the desired power supply. It is necessary to light the gas each time and, in addition, the gas flame has to be monitored so that no unconsumed gas is able to escape. The supply of gas is controlled by means of a magnetic valve which is controlled by means of a pulsating power control instrument.
Glass ceramic surfaces are sensitive to over-heating, but must be brought to a temperature which is as near as possible to but just below the permitted maximum temperature in order to ensure that sufficient power is transmitted through them.
In order to limit this temperature and to keep it as accurate as possible, experiments have been carried out using thermal cut-outs of the type disclosed in German Offenlegungsschrift No. 24 22 625. A thermal cut-out of this type, arranged between the radiant surface and the glass ceramic cooking surface, has not produced satisfactory results since the switching frequency is too high and unstable intermediate positions occurred with a relatively high adjustment and increase required in the contact distance and this prevents satisfactory switching and, in particular, good cooperation with the electronic control means for ignition and monitoring of the ignition.